Use of only gamma and x-ray emission spectra with G4RadioactiveDecayPhysics

Hi All,

I am currently attempting to use 133-Ba as a source in an application. I posted previously asking about how to add this functionality (Simulating 133-Ba Decay)

I am now curious to see if there is any way to limit the emission spectra to that of just the gamma and x-ray radiations.

Any and all help is greatly appreciated.


Not in an automatic way in Geant4. You could implement this using your own primary generator action. Store the Ba-133 lines and their intensities in a table, and use a random throw to pick a line for each event, then throw a random direction for the G4Gamma.

Hi @mkelsey ,

Thank you so much for your quick response. I think I may have found a work around. Since in reality the source is enclosed in plastic I placed a volume of plastic between the source and the scintillation area. I checked using my stepping action that no Auger electrons from the source penetrate into the scintillator. Does this make sense?


Yup, that’s exactly right! You’ll get a bit of degradation of the gamma and X-ray lines from traversing the plastic, but that’s not a huge deal.

Depending on your geometry, you may see an “efficiency” problem in your runs. RadioactiveDecay, of course, produces an isotropic distribution of gammas. If your detector only covers a small solid angle, most of the events you generate will be empty. We have that problem with our simulation: roughly 100k Ba-133 source events from outside our cryostat to get one event with detector hits.

Hi @mkelsey ,

Thank you so much for replying so quickly!

I also do see the “efficiency” issue, and have done my best to deal with it by placing the source as close as possible to the volumes and generating more events as well.

Thanks again for all of your help!

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